1. Field of the Invention
The present invention relates to a magnetic recording medium, a process for producing a magnetic recording medium, an apparatus for producing a magnetic recording medium, and a magnetic recording apparatus. More particularly, the invention relates to a magnetic recording medium having a protective film excellent in resistance to sliding with magnetic heads, a process for producing the magnetic recording medium, an apparatus for producing the magnetic recording medium, and a magnetic recording apparatus provided with the magnetic recording medium.
2. Description of the Prior Art
In the field of magnetic recording media, with the recent trend toward higher density of magnetic recording, recording media provided with thin film of Co-Ni-based or Co-Cr-based magnetic metals, comprising Co as the main component, formed by sputtering or plating are in increasingly wide use in practice in place of prior ones which use iron oxide. Such a newer recording medium has a film structure comprising, usually on an aluminum alloy substrate, a NiP plating film, a Cr undercoating film, the aforementioned magnetic film and a non-magnetic protective film, formed in the abovementioned order. When the surface of the film is too smooth, an adsorptive force will develop between the film and the magnetic head during stoppage, which involves the risk of making it impossible to start up the rotation of a spindle motor on which the recording medium has been mounted, or causing breakage of the magnetic head support system. Therefore, a so-called texture finishing is commonly applied, in which the surface is deliberately roughened to impart surface roughness to the surface. In one method of such texture finishing, as disclosed in Japanese Patent Application Kokai (Laid-Open) No. 2-208827, for example, the film is subjected to dry etching under DC bias voltage in an inert gas, whereby fine working is applied only to the protective film to obtain uniform surface roughness while the magnetic film is kept smooth as before. In another method, as disclosed in Japanese Patent Application Kokai (Laid-Open) No. 1-263913, island-like protuberences of nitride are arranged on the magnetic film and further a film of diamond-like carbon is provided.
The dry etching processing under DC bias voltage in inert gas have problems in that, in the etching of the surface, some of the surface structures are etched selectively, or even when the surface texture obtained is initially good, the surface characteristic is readily deteriorated by abrasion. On the other hand, the processing which comprises arranging island-like substances on the magnetic film involves the problems of having difficulty in securing reliable adhesion between the substance which forms the islands and the protective carbon film and of complication of process steps.